P416: CLONAL HEMATOPOIESIS IS COMMON IN AML LONG-TERM SURVIVORS AND MAY ASSOCIATE WITH DIABETES AND SECONDARY NEOPLASIAS, BUT NOT OTHER HEALTH OUTCOMES
Authors: S. M. Krauß, E. Telzerow, A. S. Moret, D. Richter, M. Rothenberg-Thurley, D. Görlich, M. C. Sauerland, W. E. Berdel, B. Wörmann, U. Krug, J. Braess, P. Heussner, W. Enard, W. Hiddemann, K. Spiekermann, U. Platzbecker, K. H. Metzeler
Journal: HemaSphere (2022)

Background: Clonal hematopoiesis (CH), the outgrowth of hematopoietic stem cells and their progeny with somatically acquired gene mutations, is a common phenomenon in elderly individuals without known hematological disorders. CH has been linked to an increased risk of developing myeloid neoplasia and cardiovascular diseases, resulting in higher all-cause mortality. More specifically, clonal hematopoiesis of indeterminate potential (CHIP) has been defined by hematopoietic clones with a variant allele frequency (VAF) ≥2% in the absence of hematologic disease. CH is also known to be common in patients with acute myeloid leukemia (AML) briefly after therapy, but prevalence and relevance of CH in AML long-term survivors (AML-LTS) has not been investigated so far. Aims: We aimed to study CH in a cohort of 380 AML-LTS using a targeted next generation sequencing (NGS) assay utilizing single-molecule Molecular Inversion Probes (smMIPs), and to analyze determinants of CH and its effects on somatic health outcomes. Methods: We employed smMIP-technology, which follows a hybridization-capture protocol for NGS library preparation to selectively enrich and amplify hundreds of genomic target loci covering 82 regions in 24 CH and AML-related genes in a single reaction. Unique molecular identifiers (UMIs) within probes enabled computational correction of sequencing errors to significantly increase precision of variant calls. Results: We successfully established a UMI-based smMIP NGS assay as well as a custom computational analysis pipeline to enable the reliable detection of variants ≥0.5% VAF. In whole blood specimens from 380 AML-LTS we detected CH in 61.4% of individuals, including CHIP (VAF ≥2%) in 35.8%. Stratification by treatment group, i.e. chemotherapy/autologous hematopoietic stem cell transplantation only (chemo) vs. allogeneic hematopoietic stem cell transplantation (alloSCT), revealed a significantly lower prevalence of CHIP in the alloSCT group (26.0% vs. 52.1%; p<.001). Concordantly, median VAF of CH mutations after alloSCT was significantly lower than in the chemo group (1.2% vs. 1.8%; p=.005). CHIP prevalence increased with age in the chemo group, from 21.7% (<50 years) to 70.0% (≥70 years), whereas it was independent of patient age in the alloSCT group (Figure A). Conversely, CHIP prevalence was independent from time since start of therapy in the chemo group, but increased with time after transplantation in the alloSCT group, from 18.4% (0-5 years) to 46.2% (16-18 years; Figure B). In both treatment groups, the known CHIP driver genes DNMT3A and TET2 were most frequently mutated. Notably, PPM1D (p<.001) and TP53 (p<.001) were more frequently mutated in the chemo group (Figure C). We did not detect significant differences in complete blood counts of AML survivors according to CH status. While most somatic comorbidities showed no clear association with CH status, prevalence of diabetes and development of secondary cancer after leukemia therapy were increased in patients with CH (VAF <2%), and more so in those with CHIP (Figure D). Image:Summary/Conclusion: We report a high prevalence of CH in AML long-term survivors, particular in those treated with chemotherapy without alloSCT. CHIP prevalence increases with age in patients treated with chemotherapy, and with time elapsed after transplantation in patients who underwent alloSCT. We reveal distinct mutation spectra for both groups. Although associations between CH and somatic morbidities seem to be weak overall, we found associations with diabetes and the development of secondary cancer after leukemia treatment, which warrant further exploration.